en.wikipedia.org/wiki/Filesystem_Hierarchy_Standard ah, now I know the name for the way the filesystem is organized. This always seemed like a user-hostile mess. The /usr subdirectory has no user files, /dev and /proc and /sys aren't even real files, /media is just a mount point even though we already have /dev for devices and there's a /mnt which seems completely redundant. User-space software exists in /bin but also /sbin but also /usr/bin and /usr/sbin (is it for the user or the system? which is it guys?) and finally also /opt.